@misc{oai:repo.qst.go.jp:00070880,
 author = {Jo, Jun-ichiro and Nakahara, Teppei and Aoki, Ichio and Saga, Tsuneo and Tabata, Yasuhiko and et.al and 城 潤一郎 and 中原 鉄平 and 青木 伊知男 and 佐賀 恒夫},
 month = {Sep},
 note = {INTRODUCTION:
With the recent progress of tissue engineering technology, the effects of regeneration-induction therapy of various tissues have been experimentally demonstrated in animal models. Furthermore, some clinical trials have also been successfully performed. Under these circumstances, it is strongly required to develop a non-invasive imaging method that can accurately evaluate the process of tissue regeneration and healing. Among various imaging modalities, magnetic resonance imaging (MRI), having a high spatial resolution and tissue contrast, is expected to be an optimal modality for this purpose. For the application of MRI for the monitoring of tissue regeneration, effective delivery of MRI contrast agents to the region being regenerated or repaired is essential. In this study, a new polymer-based MRI contrast agent has been designed to evaluate the therapeutic angiogenesis.
METHODS:
Gadolinium ions (Gd) and cyclic peptides containing an arginine-glycine-aspartic acid (RGD) sequence (cRGD) with an inherent affinity for the v3 integrin expressed on activated endothelial cells during angiogenesis were chemically introduced to dextran (cRGD-dextran-Gd). The amount of Gd and cRGD to dextran and the longitudinal relaxivity of cRGD-dextran-Gd were evaluated. To examine the interaction between the cyclic RGD and the v3 integrin, the fluorescein-labeled dextrans with or without the cRGD were cultured with human umbilical vein endothelial cells (HUVEC) expressing the v3 integrin.
Right femoral, external iliac, and deep femoral and circumflex arteries and veins were surgically ligated to prepare a mouse model of hindlimb ischemia. A laser Doppler analysis and histological evaluation revealed that the hindlimb ischemia was naturally healed accompanied with angiogenesis in the ischemic region without any treatments. In this study, mice 7 days after the vascular ligation were used as an angiogenesis model. MRI (T1-weighted image (T1WI)) was performed after intravenous injection of cRGD-dextran-Gd into the mice.
RESULTS AND DISCUSSION:
The amount of Gd and cRGD introduced was calculated to be 25 and 3.7 molecules for one dextran molecule, respectively. The longitudinal relaxivity of cRGD-dextran-Gd was calculated to be 5.3 sec-1mM-1, which is higher than that of Magnevist® (4.7 sec-1mM-1). The fluorescein-labeled cRGD-dextran was internalized into HUVEC to a greater extent than dextran-Gd. It is likely that the affinity of cRGD for the v3 integrin on the HUVEC surface enabled the fluorescein-labeled cRGD-dextran to strongly interact with the cells, resulting in the enhanced internalization by a receptor-mediated fashion.
The ischemic-angiogenic region was clearly enhanced in T1WI after the intravenous injection of cRGD-dextran-Gd. It was also found that the fluorescein-labeled cRGD-dextran was co-localized in the integrinv3-positive region in the ischemic-angiogenic region after the intravenous injection. Therefore, it is clearly demonstrated that the affinity of cRGD for the integrinv3 enabled the cRGD-dextran conjugates to be selectively delivered to the ischemic-angiogenic region of mice with hindlimb ischemia., 2012　World Molecular Imaging Congress},
 title = {Visualization of therapeutic angiogenesis with a polymer-based magnetic resonance imaging contrast agent},
 year = {2012}
}